SBIR 1R43AR060019 Phase II application: Protein Therapeutics for Muscular Dystrophy Principal Investigator: Takizawa, Norio Project Summary: This application requests for a Phase II project for our initial SBIR grant addressing the use of a novel protein therapeutic agent, MG53, for the treatment of muscular dystrophy (1R43AR060019). Our Phase I studies established manufacturing and formulation conditions, and provided significant proof- of-concept data for the use of MG53 in treating muscular dystrophy. This Phase II application proposed additional proof-of concept experiments in multiple dystrophy models (mouse, dog) and critical toxicology studies. This proposal will directly target the muscular dystrophies, a family of geneti disorders that generally include progressive muscle weakness due to degeneration of the muscle fibers that is linked to either fragility of the membranes that surround muscle cells or a compromised ability to reseal those membranes. An emerging concept in recent biomedical research establishes that intrinsic membrane repair/regeneration is a fundamental aspect of normal physiology and that disruption of this repair function underlies the progression of many human diseases, including muscular dystrophy. A therapeutic approach to increase the capacity of muscle cells to reseal their membranes following physiological levels of mechanical stress could address both of these mechanisms leading to improvement of the regenerative capacity in muscular dystrophy. Attempts to produce therapeutics targeting this unmet medical need have been complicated by the lack of knowledge of the molecular components involved. Recent studies show that MG53, a muscle-specific TRIM-family protein, plays an essential role in protection of skeletal and cardiac muscle cells against various types of acute injury or chronic physiological stresses. MG53 ablation results in defective sarcolemmal membrane repair with progressive muscle pathology. In an effort to translate these basic science findings into therapeutic interventions for human diseases, we have formed a biotechnology company named TRIM-edicine, Inc, based on intellectual properties discovered at UMDNJ-Robert Wood Johnson Medical School. Our research and development effort at TRIM-edicine during Phase I of this SBIR project has established methods to produce large quantities of recombinant MG53 protein purified from E. coli that retains efficient membrane repair function. Furthermore, we produced in vivo animal model data using dystrophic mdx mice to show that intravenous (IV) delivery of recombinant MG53 can repair membrane damage to skeletal muscle and ameliorate the pathology associated with muscular dystrophy. Additional in vivo data show that repetitive IV-injections of recombinant human MG53 to mice are safe and do not produce adverse effects. Other studies showed that subcutaneous injection of MG53 can be effective for therapeutic approaches as well. This project will leverage the expertise at TRIM-edicine in biologic drug development to pursue necessary studies for development of recombinant MG53 in treatment of muscular dystrophy to allow for the filing of an Investigational New Drug (IND) application with the Food and Drug Administration (FDA). This Phase II continuation project will involve a collaborative effort between TRIM-edicine and the University of North Carolina to pursue the proof-of-principle studies for the therapeutic application of MG53 in treatment of muscular dystrophy using the golden retriever model of muscular dystrophy. First, we will produce sufficient amount of recombinant dog MG53 proteins following our documented Chemical Manufacture Control (CMC) protocols. Second, we will test the efficacy and safety of the dog MG53 protein in reducing muscular pathology using a golden retriever with muscular dystrophy (GRMD) dog model. Third, upon completion of the in vivo animal model studies, the selection of animal species for the toxicology studies will be determined upon consultation with FDA in a pre-IND meeting. Completion of the safety/toxicology evaluations will provide the final step in preparation for filing of an IND application testing the use of recombinant MG53 in treatment of muscular dystrophy in human patients.